@Beta public final class Hashing extends Object
HashFunction
instances, and other static
hashing-related utilities.Modifier and Type | Method and Description |
---|---|
static HashCode |
combineOrdered(Iterable<HashCode> hashCodes)
Returns a hash code, having the same bit length as each of the input hash codes,
that combines the information of these hash codes in an ordered fashion.
|
static HashCode |
combineUnordered(Iterable<HashCode> hashCodes)
Returns a hash code, having the same bit length as each of the input hash codes,
that combines the information of these hash codes in an unordered fashion.
|
static int |
consistentHash(HashCode hashCode,
int buckets)
Assigns to
hashCode a "bucket" in the range [0, buckets) , in a uniform
manner that minimizes the need for remapping as buckets grows. |
static int |
consistentHash(long input,
int buckets)
Assigns to
input a "bucket" in the range [0, buckets) , in a uniform
manner that minimizes the need for remapping as buckets grows. |
static HashFunction |
goodFastHash(int minimumBits)
Returns a general-purpose, non-cryptographic-strength, streaming hash function that
produces hash codes of length at least
minimumBits . |
static HashFunction |
md5()
Returns a hash function implementing the MD5 hash algorithm by delegating to the MD5
MessageDigest . |
static HashFunction |
murmur3_128()
Returns a hash function implementing the
128-bit murmur3 algorithm, x64 variant (little-endian variant), using a seed value
of zero.
|
static HashFunction |
murmur3_128(int seed)
Returns a hash function implementing the
128-bit murmur3 algorithm, x64 variant (little-endian variant), using the given seed
value.
|
static HashFunction |
murmur3_32()
Returns a hash function implementing the
32-bit murmur3
algorithm (little-endian variant), using a seed value of zero.
|
static HashFunction |
murmur3_32(int seed)
Returns a hash function implementing the
32-bit murmur3
algorithm (little-endian variant), using the given seed value.
|
static long |
padToLong(HashCode hashCode)
If
hashCode has enough bits, returns hashCode.asLong() , otherwise
returns a long value with hashCode.asInt() as the least-significant
four bytes and 0x00 as each of the most-significant four bytes. |
static HashFunction |
sha1()
Returns a hash function implementing the SHA-1 algorithm by delegating to the SHA-1
MessageDigest . |
static HashFunction |
sha256()
Returns a hash function implementing the SHA-256 algorithm by delegating to the SHA-256
MessageDigest . |
static HashFunction |
sha512()
Returns a hash function implementing the SHA-512 algorithm by delegating to the SHA-512
MessageDigest . |
public static HashFunction goodFastHash(int minimumBits)
minimumBits
. Users without specific
compatibility requirements and who do not persist the hash codes are encouraged to
choose this hash function.
Warning: the implementation is unspecified and is subject to change.
IllegalArgumentException
- if minimumBits
is not positivepublic static HashFunction murmur3_32(int seed)
public static HashFunction murmur3_32()
public static HashFunction murmur3_128(int seed)
public static HashFunction murmur3_128()
public static HashFunction md5()
MessageDigest
.public static HashFunction sha1()
MessageDigest
.public static HashFunction sha256()
MessageDigest
.public static HashFunction sha512()
MessageDigest
.public static long padToLong(HashCode hashCode)
hashCode
has enough bits, returns hashCode.asLong()
, otherwise
returns a long
value with hashCode.asInt()
as the least-significant
four bytes and 0x00
as each of the most-significant four bytes.public static int consistentHash(HashCode hashCode, int buckets)
hashCode
a "bucket" in the range [0, buckets)
, in a uniform
manner that minimizes the need for remapping as buckets
grows. That is,
consistentHash(h, n)
equals:
n - 1
, with approximate probability 1/n
consistentHash(h, n - 1)
, otherwise (probability 1 - 1/n
)
See the wikipedia article on consistent hashing for more information.
public static int consistentHash(long input, int buckets)
input
a "bucket" in the range [0, buckets)
, in a uniform
manner that minimizes the need for remapping as buckets
grows. That is,
consistentHash(h, n)
equals:
n - 1
, with approximate probability 1/n
consistentHash(h, n - 1)
, otherwise (probability 1 - 1/n
)
See the wikipedia article on consistent hashing for more information.
public static HashCode combineOrdered(Iterable<HashCode> hashCodes)
IllegalArgumentException
- if hashCodes
is empty, or the hash codes
do not all have the same bit lengthpublic static HashCode combineUnordered(Iterable<HashCode> hashCodes)
IllegalArgumentException
- if hashCodes
is empty, or the hash codes
do not all have the same bit lengthCopyright © 2010-2012. All Rights Reserved.